1. Field of the Invention
The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery having an improved structure to prevent short-circuiting.
2. Description of the Prior Art
Recently, compact and light electronic devices such as cellular phones, laptop computers, camcorders and the like have been actively developed and produced. These portable electronic devices contain a battery pack to be operable without being plugged into an electrical outlet. The battery pack is provided with at least one battery therein so as to output a certain level of voltage to drive the portable electronic device for a given duration.
Battery packs have been developed to use rechargeable secondary batteries. Representative secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, lithium batteries, and lithium ion batteries, etc.
Lithium secondary batteries have been rapidly developed because their energy density per unit weight is high, and their operation voltage is 3.6V, which is three times higher than nickel-cadmium batteries or nickel-hydrogen batteries.
In such a lithium secondary battery, an anode active material is made primarily from lithium-based oxide, while a cathode active material is made of carbon material. Generally, lithium secondary batteries can be classified into liquid electrolyte batteries and polymer electrolyte batteries based on the electrolyte used. Accordingly, batteries using a liquid electrolyte are referred to as lithium ion batteries, while batteries using a polymer electrolyte are referred to as lithium polymer batteries. Further, lithium secondary batteries are manufactured into various types, for example cylindrical types, polygonal types and pouch types.
Typically, a lithium secondary battery includes an electrode assembly having an anode electrode plate coated with an anode active material, a cathode electrode plate coated with a cathode active material and a separator interposed between the anode and cathode electrode plates to prevent electric short-circuiting and to allow only lithium ions to move. A typical lithium secondary battery also includes a case for receiving the electrode assembly, and electrolyte injected into the case for the lithium secondary battery for allowing the lithium ions to move. In the typical lithium secondary battery, the electrode assembly has a jelly-roll configuration.
The electrode assembly is manufactured by sequentially stacking and rolling the anode electrode plate coated with the anode active material and having an anode tap connected thereto, the separator, and the cathode electrode plate coated with the cathode active material and having a cathode tap connected thereto.
Next, the electrode assembly is inserted into the case. Then the insulation case is assembled with the case so as to be seated on the electrode assembly. After the cap assembly is coupled to the case, electrolyte is injected into the case. Then, the case is sealed, and manufacture of the lithium secondary battery is complete.
However, in the lithium secondary battery as described above, since the cap assembly is separate from the insulation case, movement of the insulation case may be caused by external impact, such as by dropping the battery. The movement of the insulation case applies pressure to the electrode assembly, thereby causing an electric short-circuit between the anode and cathode electrode plates of the electrode assembly.